Mechanical and optical behavior of a novel optical fiber crack sensor and an interferometric strain sensor

The proper interpretation of measurements from an optical fiber sensor requires a full understanding of its mechanical response to external action and the corresponding change in optical output. To quantify the mechanical behavior it is necessary to know the mechanical properties of the fiber coatings. A new method for measuring the coating stiffness directly on the fiber uses nano-indentation. Special sample preparation and testing procedures were developed for the measurement of very low modulus materials using the Nano Indenter II. Results are obtained for two different acrylate coated optical fibers, namely Corning SMF28 and 3M FS-SN-4228. These results are used in understanding the behavior of the novel crack sensor and of an interferometric strain sensor. A distributed crack sensor that does not require prior knowledge of crack location and employs a small number of fibers to monitor a large number of cracks is developed. The basic design of the sensor is a polymer sheet containing an inclined fiber that is coupled to a structure. The sensor principle is that cracking in the structural member leads to cracking in the polymer sheet which induces fiber bending leading to signal loss. Monitoring the backscattered signal provides crack opening size and location. A theoretical model for optical fiber loss prediction is developed based on a combination of mechanical and optical analyses.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Olson, Noah Gale, 1969-

Advisor dc:contributor.advisor

• Christopher K.Y. Leung.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29259

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29259